Results 1 to 7 of 7

Thread: Bacterial Progenitor or Viral Evolution... Largest "Living" virus found, and its huge

  1. #1
    Join Date
    May 2013
    Location
    Phuket, Thailand
    Posts
    239

    Bacterial Progenitor or Viral Evolution... Largest "Living" virus found, and its huge

    19 July 2013 by Andy Coghlan

    dn23901-4_300.jpg

    Timeline
    28404301.jpg

    They are so different from existing forms of life, they might just as well have come from outer space. Called Pandoravirus because "opening" it has released so many questions about life – this virus is unlike anything ever seen before. Plus it is twice as large as any viruses previously discovered.

    More than 90 per cent of the Pandoravirus genes are new to science and have no known counterparts in other viruses, bacteria or higher forms of life such as animals.

    Two species have been discovered. Both are egg-shaped and so big, at a micrometre long, and half that width, that they can be seen through a standard lab microscope.

    The one with the largest genome, Pandoravirus salinus, has 2.47 million DNA base pairs and came from sediments in the mouth of the Tunquen river in Chile. The other, Pandoravirus dulcis, boasts 1.9 million base pairs and came from a shallow pond near Melbourne, Australia.

    The genome of P. salinus is twice the size of that belonging to the previous record-holder, Megavirus chilensis, or mimivirus. The Pandoraviruses are also larger than many bacteria, and even some cells of plants and animals.

    Most common viruses have fewer than 10 genes, but P. salinus has 2556 genes, 93 per cent of which have no known counterparts in any other sequenced organisms. P. dulcis has 1502 genes.

    "No microorganism closely related to P. salinus has ever been sequenced," say the discoverers of the Pandoraviruses, Jean-Michel Claverie and Chantal Abergel of the CNRS, the French national research agency, at Aix-Marseille University in France. "One of our jokes is that either they are from outer space, or from a cellular ancestor that's now disappeared," says Abergel.

    My viral life

    As part of their investigation, Claverie, Abergel and their colleagues examined the life cycle of P. salinus. First, virus particles invade host amoebas. DNA from the virus then takes control of the amoeba nucleus, ordering it to make hundreds of new viral particles. After 10 to 15 hours, the host cell bursts, releasing the particles to seek out and infect new cells.

    "Pandoraviruses appear to be built through a mysterious continuous process where the core and the shell are assembled simultaneously," says Claverie.

    The Pandoraviruses qualify as viruses because they can't replicate or process their own DNA and have to rely on a host to do that for them. They have no genes for making their own energy-storing molecules, and can't make proteins. There is also no sign of the cell-like division that happens in all bacteria, eukaryotes and Archaea.

    Being able to make your own energy is a definition of life, so, like all viruses, Pandoraviruses are not strictly alive, points out Gary Foster of the University of Bristol, UK, who studies viruses that infect fungi. "It fulfils all the criteria for being a virus, except the sheer size, and that's what's blowing people's minds away," says Foster.

    Virus hunters

    Claverie and his colleagues, who are veteran hunters of giant viruses suggest that the Pandoraviruses are unique and deserve their own, new domain of life, beyond the three existing domains of bacteria, eukaryotes and Archaea.

    But Foster, who is involved in the International Committee for Virus Taxonomy, thinks it's too early for that. "If you change the domains for every new weird thing, it would be an absolute mess," he says. So for now, Foster thinks the viral definition is suitable.

    Foster believes that there may be many more weird organisms in the world, with equally weird genomes. "We just haven't looked hard enough," he says. "As we look at the extremes of life, we will find many more of these weird things."

    Claverie believes Pandoraviruses might be abundant in sediments, but haven't been found before because sediments are seldom explored. "As far as we know, this is the first recovery of viruses from sediments," he says. "They're probably everywhere, and we're actively looking for them."

    As to the evolution of the Pandoraviruses, Claverie thinks the most likely explanation is that they were once self-supporting cells, but downsized themselves to viruses by becoming parasites, jettisoning all the genes they formerly needed to process DNA and make their own energy and relying instead on the corresponding machinery in their new hosts.


    Life began with a planetary mega-organism
    Life began with a planetary mega-organism - life - 25 November 2011 - New Scientist


    4th domain of life...
    Biology's 'dark matter' hints at fourth domain of life - life - 18 March 2011 - New Scientist
    "Truly I was born to be an example of misfortune, and a target at which the arrows of adversary are aimed"

  2. #2
    Join Date
    Sep 2009
    Posts
    679
    In my opinion, rather than have a list of required qualities, if you have any of the following qualities, you have life:

    • Self replicates
    • Evolves (Darwinian)
    • Did evolve (Darwinian) to get to its current form
    • Has thought

    Since we are confined to one small rock within a vast cosmos, there are undoubtedly many other bullets to this list that I can't possibly imagine. Maybe someone else can?

  3. #3
    Join Date
    May 2013
    Location
    Phuket, Thailand
    Posts
    239
    Quote Originally Posted by Databed View Post
    In my opinion, rather than have a list of required qualities, if you have any of the following qualities, you have life:

    • Self replicates
    • Evolves (Darwinian)
    • Did evolve (Darwinian) to get to its current form
    • Has thought

    Since we are confined to one small rock within a vast cosmos, there are undoubtedly many other bullets to this list that I can't possibly imagine. Maybe someone else can?
    Internal energy production would be a requirement. Thought would only be for a small group of multicellular mega fauna as well.
    "Truly I was born to be an example of misfortune, and a target at which the arrows of adversary are aimed"

  4. #4
    Join Date
    Sep 2009
    Posts
    679
    Quote Originally Posted by Hdreams View Post
    Internal energy production would be a requirement.
    Why?


    Quote Originally Posted by Hdreams View Post
    Thought would only be for a small group of multicellular mega fauna as well.
    Again, why? Why even require a cell? Geez, like you've never even seen an episode of Star Trek.

    I think we are way too narrow in our assumptions about what life must be. Viruses have no internal energy production yet they no doubt have the potential to evolve into something that is obviously life by any standards. Even something as simple as a prion has the potential to take on a form that is obviously life by any standards - they replicate and evolve and therefore the potential is there. If we want to arbitrarily draw a line and define life as something that has crossed it, fine. I just think that is a very unimaginative and closed minded thing to do.

  5. #5
    Join Date
    May 2013
    Location
    Phuket, Thailand
    Posts
    239
    Quote Originally Posted by Databed View Post
    Why?
    Internal energy production would be a requirement of any significant life above a viral level. Any complex life, i.e multi-cellular or complex single cell requires a source of energy, whether it be photosynthetic, mitochondrial etc..in design.



    Quote Originally Posted by Databed View Post
    Again, why? Why even require a cell? Geez, like you've never even seen an episode of Star Trek.

    I think we are way too narrow in our assumptions about what life must be. Viruses have no internal energy production yet they no doubt have the potential to evolve into something that is obviously life by any standards. Even something as simple as a prion has the potential to take on a form that is obviously life by any standards - they replicate and evolve and therefore the potential is there. If we want to arbitrarily draw a line and define life as something that has crossed it, fine. I just think that is a very unimaginative and closed minded thing to do.
    I agree our perceptions of life may well be too narrow.. Life outside of a cellular basis may exist but we have nothing but speculation of it (Viral life omitted). I agree with you on the viral side, but virus's also need cellular life to survive as they dont have the capacity to replicate themselves. So viral life, at least as we know it also presupposes the presence of cellular life.
    "Truly I was born to be an example of misfortune, and a target at which the arrows of adversary are aimed"

  6. #6
    Join Date
    Sep 2009
    Posts
    679
    Quote Originally Posted by Hdreams View Post
    Internal energy production would be a requirement of any significant life above a viral level. Any complex life, i.e multi-cellular or complex single cell requires a source of energy, whether it be photosynthetic, mitochondrial etc..in design.

    I agree our perceptions of life may well be too narrow.. Life outside of a cellular basis may exist but we have nothing but speculation of it (Viral life omitted). I agree with you on the viral side, but virus's also need cellular life to survive as they dont have the capacity to replicate themselves. So viral life, at least as we know it also presupposes the presence of cellular life.
    Well now were talking significant life above an arbitrary level. This is what I was talking about - we are stuck thinking that life must be significantly like us, as in, our preconceptions of what life must be. There are two terms being tossed around when you have this debate: life and alive. I assert they are very different. To call something alive means that it is dynamic in nature, metabolizes energy, it grows, etc. Anything alive is obviously life, but what about something that is on its way, evolutionarily speaking, to becoming alive? If we don't consider a self replicating molecule by itself necessarily life, at which point did the replicating molecule that led to life on Earth become life then? I think you can have life, without anything being alive.

    Look at it this way. Say you went to a planet and it was covered in an ooze of extremely simple self replicating molecules, say as simple as a dozen or so monomers strung together in just the right way to assemble naturally occurring amino acids into some protein that then naturally breaks down into the form of the parent molecule. Not too crazy right? This would be something millions of times simpler than a virus and nothing more than chemistry. Do we then turn around and send the message back home, "Nope, no life here, let's move on." I don't think so. We will claim we have found life.

    Now, you can claim that by acquiring naturally occurring molecules that this is in some form the harvesting of energy in the form of chemical bonds, or in the form of whatever naturally causes these bonds to break and I will agree that any process, whether we call it life or not, must obey the laws of thermodynamics, but I don't think this qualifies as internal energy production any more than a virus undergoes internal energy production. It just happens because of the particular mixture of chemicals, monomers, polymers, heat, water, radiation, etc. Further, when you look at any process of metabolism in any life form at the microscopic level, you will find that a very complicated, extremely large series of the exact same types of process are occurring; however, in the case of mega fauna or even single cell organism, there is an organism controlled flow of energy precisely tuned to keep the organism alive.

    As to your comment about requiring speculation, if we accept that a virus is life, then no speculation is required to believe in non-cellular life. If we don't accept a virus as life, what's so bad about speculation anyway? It's the lack of imagination that continuously causes scientists to be surprised when they discover something they had assumed was impossible. This happens all the time.

  7. #7
    Join Date
    May 2009
    Posts
    3,718
    I look at viruses as like a seed, it is not alive until it falls into a suitable environment then it starts to grow and becomes alive. I don't think anyone would say that an apple seed is alive or that an apple tree is not alive.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •